There has been an embarrassing blow to the prosecution's case in the Casey Anthony trial.

A prosecution witness testified that chloroform found in Casey's car could have come from, of all things, cleaning fluid.

"These levels are equal to what you might find in a common cleaning product?" asked Casey's attorney, Jose Baez.

"Yes, from my experience those levels have been detected in substances that have been used for cleaning products, yes," said FBI forensic chemist Michael Rickenbach.

His testimony directly contradicts another prosecution expert who testified Monday that he found significant levels of chloroform in the car.

"The chloroform was shockingly high. Unusually high," Dr. Vass testified a day earlier.

But the FBI chemist said that he found only tiny amounts of chloroform and some tests found none at all.

"It wasn't the most chloroform you'd ever seen in twenty years, was it?" asked Baez.

"It was not the most chloroform I've seen in twenty years no," said Rickenbacher.

"And it's not what you would call shockingly high levels of chloroform would it?" Baez asked.

"No, it's not," he said.

"That puts a big wrench into the prosecution's case that maybe Casey used chloroform to kill her daughter Caylee or knock her out before killing her. So it's a huge blow to the prosecution today, big points for the defense," says Aphrodite Jones of True Crime with Aphrodite Jones.